Polypeptides and proteins have limited modes of administration. Transdermal or oral delivery is difficult because of the sheer size of proteins and polypeptides (&gt;7,000 MW) and their instability in the gastrointestinal environment. In general, protein drugs are administered either by subcutaneous (s.c.) or intravenous (i.v.) injection usually in hospital or clinical settings. Proteins (&lt;30,000 mw) injected s.c. or i.v. have serum half lives in duration of hours. Limitations in the mode of administration and serum half-life have limited the utility of protein therapeutics. There is a need for more effective and well-tolerated methods for the delivery of proteins and peptides. A possible mode of administration of a protein is via the lungs. There is a need for novel and effective methods for delivering therapeutic proteins to the lungs.